Last week, one possible long-term solution was introduced by Senator Tom Carper (D-DE). The Senator introduced a bill that would increase the federal gas tax to about 30 cents per gallon and the diesel tax to 40 cents per gallon by 2019 and adjust them for inflation going forward. In addition, this plan would expand both the Earned Income Tax Credit and the Child Tax Credit.

Back in February, we modeled a very similar plan to this: raise the gas tax to $0.28 per gallon, adjust it for inflation going forward, and increase the earned income tax credit by $15 billion each year. The $0.28 gas tax would completely fund the highway trust fund in the next decade with a small negative impact on the economy (0.1 percent reduction in GDP). We found that a straight gas tax increase would disproportionate impact low- and middle-income tax payers, who spend more on gasoline as a percent of their income.

Note: Gas tax modeled is approximately $168 billion over the next decade. Numbers represent the change in after-tax income from what it would have been in the absence of each tax change. For example, taxpayers in the top quintile have 0.25% lower after-tax incomes over the long run than they otherwise would have in the absence of the tax change.

The Highway Trust Fund is a government program that largely adheres to the benefit principle by matching cost (gas tax) with benefits (improved roads). This structure should remain. However, a straight gas tax increase would have a slight impact on economic growth, disproportionately tax the bottom two quintiles of income earners, and have political implications. To address these concerns, any increase in the gas tax could be offset by a tax cut of an equal dollar amount. An increase in the gas tax paired with an EITC expansion is a reasonable way to accomplish this.

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